I'm trying to come up with a list of games, preferably F2P or very cheap, that are still playable at moderate latency - so this American can play them with his European friends. I've had several recommendations for L4D2, and Minecraft would be great if it wasn't $25.

I figured I'd ask here and see what other suggestions people had.

I've recently tried playinghttp://store.steampowered.com/app/230410/, which is a f2p cooperative third person shooter. The gameplay's quite fun, though the mission objectives are really bland. Also you can't go wrong with http://store.steampowered.com/app/209870/